Small toy figures with laptops and smartphones are seen in front of displayed Viasat Internet logo. File/Reuters

The digital assault against Viasat's KA-SAT network in late February took place just as Russian armour pushed into Ukraine. US Secretary of State Antony Blinken said the cyberattack was intended "to disrupt Ukrainian command and control during the invasion, and those actions had spillover impacts into other European countries".

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British Foreign Secretary Liz Truss called the satellite internet hack "deliberate and malicious" and the Council of the EU said it caused "indiscriminate communication outages" in Ukraine and several EU member states.

The Viasat outage remains the most publicly visible cyberattack carried out since Russia's invasion of Ukraine, in part because the hack had immediate knock-on consequences for satellite internet users across Europe and because the crippled modems often had to be replaced manually.

US Secretary of State Antony Blinken speaks during a press conference. File photo

"After those modems were knocked offline it wasn't like you unplug them and plug them back in and reboot and they come back," the US National Security Agency's Director of Cybersecurity Rob Joyce told Reuters on the sidelines of a cybersecurity conference on Tuesday.

"They were down and down hard; they had to go back to the factory to be swapped out."

The precise consequences of the hack on the Ukrainian battlefield have not been made public, but government contracts reviewed by Reuters show that KA-SAT has provided internet connectivity to Ukrainian military and police units.

British Foreign Secretary Liz Truss arrives for a meeting. File photo

In a statement, Ukraine's State Service of Special Communications and Information Protection said that Russia "is an aggressor country attacking Ukraine not only on our land, but in cyberspace too".

The Russian Embassy in Washington did not immediately return a message seeking comment. Russia routinely denies it carries out offensive cyber operations.

Reuters